We have developed a drop-on-demand printhead that can eject molten metal droplets. The capability to eject solder drops on an X-Y stage controlled substrate makes this new technology ideal for fast prototyping of metallic traces on planar and 3-D objects. The ejection of the conducting droplets is accomplished by the electromagnetic expulsion between two opposite flowing currents. One current path flows through the molten metal such as solder, the other through a copper stripe. The electrical connection between the two conductors was accomplished by two Ni plated vias. The expulsion force experienced between the two conductors causes the solder to squirt out of a nozzle. The size of the ejected solder drop depends on the driving energy, which was controlled by both the pulse width and the drive voltage. For successful operation of the printhead, wettability of the solder to the printhead material needs to be taken into consideration. We have constructed the solder jet printhead in both a polyimide laminates and a ceramic form that can withstand a much high temperature than the polyimide. We have ejected molten PbSn eutectic solder as well as BiSn and InSn with precision on Si wafers, over substrates with different height and connecting the traces on different levels, as well as creating free standing 3-D structures.